A well-known way of cutting tubular workpieces into desired lengths is to shear or sever the tubing by a guillotine-type operation. Basically, this involves clamping the tubing between a set of jaws to hold it stationary and driving a knife through the tubing in a plane perpendicular to the longitudinal axis of the tubing and between the jaws. A device of this class is disclosed in U.S. Pat. No. 3,273,433 to Alexander Borzym.
As a practical matter, the stroke length or penetration depth of the cutoff is limited by the point at which the knife holder meets the clamping jaws. It is desirable to maximize stroke length so that the knife edge can be reground several times, each such regrinding having the effect of shortening the knife length available to penetrate the workpiece. On the other hand, penetration depth cannot be gained at the expense of lateral support for the knife since sufficient lateral loading is produced in the typical shearing operation to break off an inadequately supported knife.